In a birefringent crystal, an incident light ray will separate into two rays, which may travel in different directions. The direction in which the light travels is dependent on its polarization. For example, the light will travel in different directions for each of two perpendicular states of polarization. Some types of crystals naturally are birefringent. In other types of crystals, application of sufficiently a high voltage across the crystal induces birefringence. The induction of birefringence in a crystal is referred to as the “electro-optical effect,” and a crystal processed to provide the electro-optical effect in an optical system is referred to as an “electro-optical device.”
Two fairly common types of electro-optical devices are a Pockels cell and an electro-optical deflector. “Pockels cell” refers to a type of crystal having an angle of refraction that shifts by 90 degrees when a sufficient voltage is applied across the crystal. Accordingly, Pockels cells are particularly adapted to function as optical switches having two states (e.g., “on” and “off”). In contrast to a Pockels cell, an “electro-optical deflector” refers to a type of crystal having an angle of refraction that varies based on the voltage applied across the crystal. In some cases, micro-radian angle changes can be achieved through slight voltage variations. Electro-optical deflectors are particularly adapted to function as light beam steering devices.
In order to produce an electro-optical effect in a Pockels cell or an electro-optical deflector, an optical system includes at least one electro-optical device driver adapted to provide a voltage across the electro-optical device. Traditional electro-optical device drivers are configured differently, depending on whether they are to provide an output voltage to a Pockels cell or to an electro-optical deflector. For example, a Pockels cell driver typically is configured to provide a single-polarity (e.g., positive or negative) output voltage at a pre-determined value, whereas an electro-optical deflector typically is configured to provide a single-polarity output voltage having a value that may be varied. Either way, traditional electro-optical device drivers include capacitive elements within which charge is built up and stored, in order to provide the output voltage. Pulse width modulation (PWM) often is used to build up the charges within the capacitive elements, and the charge may be discharged when it is coupled to the electro-optical device. Voltages sufficient to produce an electro-optical effect typically are relatively high (e.g., in a range of about 500-4000 volts (V) or more).
Although existing electro-optical device drivers provide adequate functionality in many cases, they also suffer from some disadvantages relating to safety, size, frequency limitations, and power consumption. Regarding safety, the retention of energy in the capacitive elements gives rise to certain safety and handling issues. In particular, during handling of a driver, extreme care should be exercised in order to avoid discharging the energy into an unintended load. Regarding size, electro-optical device drivers that provide variable voltages tend to be expensive, relatively large electronics modules. For example, a typical, variable voltage, electro-optical device driver may be implemented as a rack-mounted module having dimensions in a range of about 45-60 centimeters (cm) in width and depth, and about 5-10 cm in height. Regarding frequency limitations, the rate of a PWM input to charge the capacitive elements is limited to avoid output voltage droop. Correspondingly, the rate at which the output voltage may be switched on and off also is limited. Regarding power consumption, existing electro-optical device drivers continue to consume power, even at times when the output voltage is not provided to the load, because these drivers continue to maintain the energy within the capacitive elements during those times. Accordingly, these electro-optical device drivers tend to be relatively inefficient, with regard to power consumption.
For at least these reasons, it is desirable to provide relatively compact and safe electro-optical device drivers, which are adapted to operate at high switching frequencies, and which are energy efficient. Other desirable features and characteristics of embodiments of the inventive subject matter will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and the foregoing technical field and background.